This invention relates to monitoring and control systems. More specifically, the invention relates to a fail-safe redundant linkage and sensor assembly for sensing forces applied to the linkage while maintaining functionality of the linkage.
In connection with issues discussed in an article entitled "Safety Board Debates 737 Rudder Fixes", Aviation Week & Space Technology, Mar. 23, 1999, pp. 26-27, there is considerable discussion as to the possibility and probable cause of a 737 rudder control system failure. In order to more clearly ascertain the causes of problems, if any, which may arise in the future, it is considered desirable to monitor the forces applied to a certain control linkage. However, it is also important that the mechanical strength of the linkage not be impaired.
One way that this may be accomplished is to attach conventional strain gauges to the linkage. However, the strain engendered by the forces involved (in the range of zero to several hundred ponds) in linkages deemed adequate from a structural standpoint, is quite small. Problems of obtaining sufficient signal to noise ratio with conventional strain gauges, as well as problems of de-lamination and drift of such gauges over time, makes sensing forces with such conventional gages problematic. For at least these reasons an alternative to sensing force by means of conventional strain gages is desirable.